Despite my complete lack of knowledge when I bought my boat, and the post hoc decision that the guy who sold it to me was just out to make a buck, I managed to get a great boat that has apparently spent more time on a trailor than in the water. Ergo, she had a mercifully solid deck. I filled and drilled all holes in the deck last year and found zero sponge if not a little bit of dry rot. Because of this success, I managed to convince myself the transom was in good shape and didn't pull any bolts to confirm or deny it. So this fall when I took her apart to start getting ready for a paint job, I was horrified to see sponge on the lower bolts.
As chronicled here, I went through several stages of grief as I discovered the amount of damage to the transom core. At this point I think it is important to acknowledge the psychological forces at play here. I consider myself a pretty stringent adherent to reality (excepting when I choose to intentionally alter reality, but that's a different story), however at first I wanted to believe, despite evidence to the contrary, that my core only had spotty issues.
I purchased a dremel knock-off from northern tool and began cutting into the transom from inside the lazarette where I would spend many a crooked hour. Cutting out 4x4 sections, I started to convince myself that the damage was isolated to a few sections. Although this was partly true and confirmed that my boat has never sat at a slip for any amount of time, the reality was that it was necessary to cut the whole lot out. Unfortunately, I did not take any pictures at this time as I was still in deep denial of my future.
When you see rot, it is obvious. You will not need to run back to the computer to confer with your virtual friends whether or not the balsa is gone. It will be black not blonde, and at it's worse it will be possible to wring water from it. My advice to everyone is this: Make a few exploratory drilling holes and decide if there is water present. Basically, if there is standing water anywhere, the whole thing is toast. Particularly if there is dark wood in multiple spots. I did find areas where the wood was in great shape and adhered very well to the outer skin, but this was the minority. If you find several spots, just accept your fate and go industrial on the thing. The faster you recognize your predicament, the faster you will be done.
Don't use a Dremel. It is much too slow and I burned out one just trying. The thing you want is a 3 inch cut off tool. I got mine from harbor freight because it was cheap and fiberglass is hell on electrical points. I taped a piece of paper towel around the air intake to try and reduce the amount of dust that got in. I spent hours with the dremel and was pretty much done when I switched to the cut off tool. Take advantage of my pain and just buy the cut off tool.
Make your cuts in whatever shape that pleases you, but a grid of two inch squares worked for me. Then I used a chisel and a mallet to pop off the pieces with varying levels of success. It was essential to use a mirror in the bottom of the lazarette to see what I was doing. I rarely put my head into the compartment, using the mirror as my eyes as well as a lot of feeling around. This part sucks, though it is possible to chip it all out eventually. Here is a pick of the transom with all the core removed.
- tran in clean.JPG (23.49KiB)Viewed 14086 times
I bought some marine grade plywood that was 3/8” thick. That was what they used originally and despite my thoughts of increasing the thickness, I was happy in the end that I kept it original since the finished product was flush with the original dimensions. I used a piece of cardboard to make a stencil that was easier to work with. I started on the outside of the boat to get the shape of the curve, then put it inside and roughly cut out an approximate shape of the hole.
I transcribed the stencil onto my piece of wood and cut the shape. I dry fit the wood several times into the slot and had to make some additional cuts, but this process was easier than I expected. Once to shape, I dry fit the new core and started bolting to the hull. I drilled additional holes to make sure the entire core was evenly pressured up against the outer skin. The wood started making cracking noises as I tightened the bolts because the curve was too great.
To allow the bend that is required to adapt to the hull form, I cut relief lines in the core. These also work as slots for the epoxy (I know there is a name for this, but it escapes me now). Finally, I drilled oversized holes for every hole that would later have a bolt. Rather than try to chip out brand new wood after installation, it seemed simpler to cut it now, then fill with epoxy later. This should eliminate any future intrusion of water into the core.
- trans wood core.JPG (25.04KiB)Viewed 14086 times
I left the bolts tight for about three weeks as I had a trip to Spain for work that interfered. Despite that amount of time, the bolts came off no problem. I did have to chip off some of the washers, but overall it was easier than I expected. Wiping down with lots of solvent to get rid of any leftover oil I was ready for the inner skin.
I ordered some biaxial fiberglass mat and some fiberglass cloth from Jamestown Distributors. Mixing up some epoxy with colloidal silica I spread it all over the core and laid up the biaxial mat I had cut to shape using my old cardboard template. Anticipating the mat to slide down the vertical surface, I had my staple gun at the ready and put a couple staples in for good measure. Biaxial mat is really nice to work with. My initial intent was to alternate layers of biaxial mat with fiberglass cloth, but I had a terrible time getting the second layer of cloth to stay up even long enough for me to put a staple in. It was infuriating and again I had wished I had used slow hardner.
Hindsight: I would still use fast hardner as it will prevent the layers from sagging as the early layer hardens up. However, don't bother with the cloth, it is useless on vertical surfaces, particularly with limited access. I switched to biaxial mat and was back on track with still some frustration of it staying vertical. I was able to get a staple into it and then wet it out throughly. Success!
Despite using every last drop of resin I had, I was able to get the second piece of mat installed and felt good about the overall skin thickness. I did use slow hardner on the second layer and was glad as blisters appeared over several hours that were able to be squished out. While laying up, I had to cut relief cuts in the mat that lay on the bottom of the boat where the curve was greatest, though once saturated, these overlaps were impossible to see. Overall, I was ecstatic with the outcome and feel like this project was well worth my time. It came out looking great and I am much more confident it the strength of the transom.
- transom finished.JPG (17.39KiB)Viewed 14086 times
Cheers,
Kuriti